1. Field of the Invention
The present invention relates to a method for manufacturing a steel mold, and more particularly to a method for manufacturing a steel tire mold.
2. Description of Related Art
Generally, tires are manufactured with steel molds, and the mold is composed of several parts. A tire has a tread to increase the friction between the tire surface and ground, two sidewall plates and bead rings. Consequently, with reference to FIG. 3, a tire mold (30) comprises two half shells (31, 312). With reference to FIGS. 3 and 4, the half shell (31) may be composed of a single part, or the half shell (31xe2x80x2) may be composed of several parts. The half shells (31, 312) have a tread design (32) and the characters and designs on the sidewall. The characters and designs on the sidewall add to processes and increase the complexity in manufacturing a tire mold.
With reference to FIG. 5, a conventional method of manufacturing a steel tire mold that has two half shells includes the following steps:
selecting a suitable material for the tire mold such as low-carbon steel or medium carbon steel;
cutting and shaping the material into different shapes on a lathe;
boring alignment and assembly holes into the parts of the half shell (31xe2x80x2) to align and mate the mold parts;
assembling the parts into a steel half shell (31xe2x80x2) to form a semi-finished tire mold;
manually cutting a tread design in the assembled steel half shell (31xe2x80x2);
manually cutting characters, designs, etc. in the sidewall of the assembled steel half shell (31xe2x80x2); and
dressing the surface of the half shell (31xe2x80x2) to remove burrs and fine finishing the shape of the half shell (31xe2x80x2) to meet the design requirements.
Through the application of the preceding steps, a finished steel tire mold is composed of two half shells and available for manufacturing tires.
Machines are used to perform all the steps described except cutting the tread design and the characters, designs, etc. In conventional methods, the tread and the characters and designs content are manually cut in these two steps, and the manual operations are not easy. The conventional methods of making steel molds for tires include the following shortcomings.
1. Long Production Time for the Mold
Generally, the tread design is complex and the carbon steel is hard to cut with hand tools so that the manufacturing time for the mold is long and slow.
2. More Employees
The manual operations require a skilled worker for each process. Since a skilled worker can only work one piece at a time, many skilled workers are required to simultaneously manufacture multiple molds.
3. Precision of the Finished Product is Limited by the Skill of the Worker
Hand cutting tools are extremely difficult to control precisely on a repeated basis. There is an inherent limitation to the precision of handmade pieces, and the precision of individual pieces is dependent on the talent and training of the worker and the time available. Generally speaking, handmade pieces are not as good as machine-made work pieces.
4. Noise Pollution
The handmade cutting causes noise that is potentially harmful to humans and pollutes the surrounding environment when workers cut the tread design and the character content for the mold.
5. High Production Cost
Because of the extensive manual operations, the production cost will be high, and the factory will lose competitiveness in business.
Therefore, a machine-made process must be developed to overcome the shortcomings. The present invention provides an improved process for manufacturing steel tire molds to mitigate and/or obviate the aforementioned problems.
A method for precisely and quickly manufacturing steel tire molds that have at least two half shells is provided.
The shapes of the half shells are designed with CAD software, and CAM software uses the CAD files to develop files and parameters for an electric discharge machine (EDM) and computer numerical controlled (CNC) engraving machines, drilling machines and lathes. After selecting an appropriate mold material such as low-carbon steel or medium carbon steel, the CNC lathe turns the materials into different designed parts of the mold. To ensure that these parts are aligned and assembled properly, location and positioning holes are bored in the mold parts using a boring process. The parts are assembled to form the half shell of a tire mold in an assembly process. An electric discharge machining (E.D.M.) device with a copper electrode that is shaped by the CNC drilling machine cuts the tread design in the half shell. Than, the CNC engraving machine cuts the characters and designs designed with CAD and CAM software into the half shell sidewalls. Finally, the half shell surface is dressed to remove any burrs to make a finished product.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.